Internal pocket fastener system for ceramic matrix composite heat exchanger

ABSTRACT

A fastener system provides an internal pocket within a CMC HEX panel into which a fastener stud is inserted through an internal pocket opening and loaded to secure the CMC HEX panel to a support structure.

BACKGROUND OF THE INVENTION

The present invention relates to a fastener system, and more particularly to a fastener system which secures a composite heat exchanger panel to a support structure.

Aerospace/industrial gas turbine engine (GTE) applications and hypersonic propulsion systems include several component assemblies which are exposed to high temperatures. Among these component assemblies are combustion chambers, exhaust nozzles, afterburner liners and heat exchangers (HEX). These component assemblies may bound a portion of a gas path that directs the combustion gases through the engine and are often constructed of heat tolerant materials. Ceramic matrix composites (CMCs) are one class of materials which possess the requisite heat tolerance properties for these applications. CMCs typically include materials of carbon or silicon carbide fibers in a carbon or silicon carbide matrix.

Although CMC components provide significant heat tolerance properties, the CMC materials alone may not withstand the severe mechanical and structural demands of these applications. Often, a noncomposite support structure is utilized with the heat tolerant CMC structures to form the component assembly. The CMC structure heat shields the noncomposite support structure to maintain the noncomposite support structure within operational temperature limits.

The CMC structure is commonly secured to the noncomposite support structure with mechanical metal or composite threaded fasteners, CMC “T” joints, Miller fasteners and round braided fasteners. Although effective, each current fastener system may result in specific design constraints which need be accommodated by the component assembly. Current fastener systems may also have to contend with leakage around the fastener and tolerance control issues. Furthermore, fastener systems for certain applications may require that the fastener system be flush as any portion that may otherwise project into a combustion gas path may introduce undesirable turbulence and be subject to foreign object damage.

SUMMARY OF THE INVENTION

The fastener system according to an exemplary aspect of the present invention secures a CMC HEX panel having a multiple of fuel cooled channels to a support structure. The fastener system includes a fastener head of a fastener stud that is inserted through an internal pocket opening and rotated within an internal pocket such that the fastener stud is locked into the internal pocket formed within the CMC HEX panel. A fastener shank of the fastener stud is attached to the support structure with foot hardware and loaded to secure the CMC HEX panel to the support structure.

Gas leakage from the combustion side to the backside is minimized since the fastener head is buried in the CMC HEX panel and there is no direct path through the CMC heat panel. Since the fastener stud and the composite hot-face CMC HEX panel are independent articles, they may be processed independently and may be of different materials.

Another fastener system according to an exemplary aspect of the present invention utilizes a fastener head receivable within one of the multiple of fuel cooled channels.

Another fastener system according to an exemplary aspect of the present invention utilizes a metallic tubular liner as the fastener stud. The metallic tubular liner forms the fastener head while a multiple of extensions from the metallic tubular liner form the fastener shanks.

Another fastener system according to an exemplary aspect of the present invention may be applied to a Maintainable Composite Panel (MCP) HEX. The MCP HEX facilitates maintenance and enhances the reusability of particular components. The MCP HEX utilizes a hot-face CMC HEX panel which may be readily disassembled from a multiple of metallic coolant tubes, a thermal insulation panel and a support structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently disclosed embodiment. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1A is a general schematic view of a hypersonic aircraft;

FIG. 1B is a schematic sectional expanded view of an engine package for use with the hypersonic aircraft of FIG. 1A;

FIG. 2 is a schematic sectional view illustrating an electrical power generation system according to the present invention for use with the aircraft illustrated in FIG. 1A;

FIG. 3 is one embodiment of a fastener system for a CMC HEX;

FIG. 4A is a schematic view of a fastener stud in a disengaged position;

FIG. 4B is a schematic view of a fastener stud in an engaged position;

FIG. 5 is another embodiment of a fastener system for a CMC HEX utilizing a coolant channel as an internal fastener pocket;

FIG. 6A is another embodiment of a fastener system for a CMC HEX utilizing a metallic tubular liner as a fastener stud;

FIG. 6B is an exploded view of the CMC HEX of FIG. 6A;

FIG. 7A is another embodiment of a fastener system for an MCP CMC HEX;

FIG. 7B is an exploded view of the MCP CMC HEX of FIG. 7A; and

FIG. 7C is an assembled view of the MCP CMC HEX of FIG. 7A.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT

-   Note: I copied this section from 4685 which Mark Sillence did a good     job of editing

FIG. 1A schematically illustrates a vehicle 10. The disclosed embodiment schematically illustrates a hypersonic aircraft. Vehicles may be manned or unmanned, may be reusable or may be one-way such as warhead carrying missiles or disposable launch vehicles. The disclosed hypersonic propulsion system 18 is a dual mode gas turbine (subsonic and supersonic combustion) and supersonic ramjet engine (dual mode scramjet-DMSJ). It should be understood that other propulsion systems such a rocket based combined cycle engines and dual mode ramjet or scramjet engines or supersonics combustion ramjets (Scramjets) may also benefit herefrom.

The vehicle 10 generally includes a fuselage 12, a wing structure 14, and an empennage 16. The DMSJ propulsion system 18 is located within an engine package 20 defined in part by an underside of the fuselage 12. The engine package 20 is defined between a forward inlet 22 such as an intake structure and an aft outlet 23 such as an exhaust nozzle structure. The flowpath and flow path structure defined therebetween may be rectangular, annular (circular), elliptical, or complex in shape and may integrate at various positions with respect to the vehicle. Shock interactions and vehicle operation dictate that the DMSJ propulsion system 18 be highly integrated into the overall airframe design. The engine package 20 is placed to take advantage of the shock generated by the vehicle forebody. The flow is compressed behind the shock which increases pressure within the DMSJ propulsion system 18 so as to produce greater thrust. In addition, the aft portion of the vehicle is designed to promote expansion of the exhaust and is essentially an extension of the scramjet nozzle. That is, the entire undersurface of the vehicle may be considered to be part of the propulsion system.

Referring to FIG. 1B, the engine package 20 can be, in part, defined by a forebody 34, an isolator 36 (often integrated therewith), and an external vehicle skin structure 82. The external vehicle skin structure 82 is disclosed herein as a portion of the engine package 20 but may alternatively be at other vehicle locations. A combustor 38 is located along a scramjet flowpath F_(S) to direct a hypersonic flow between a forward inlet 21 and an aft outlet 24. A control system 40—typically a portion of the aircraft flight control system avionics—may control operation of the engine system 18 in response to one or more of sensor inputs, operator inputs, and the like.

For a turbine based combined cycle system, A gas turbine engine 42 is located along a turbine engine flowpath 44 which directs subsonic and supersonic flow F_(T) between a forward inlet 46 and an aft outlet 48 separate from the scramjet flowpath F_(S). The engine 42 is typically partially recessed into the fuselage 12 above the combustor 38. Scramjet inlet flaps 50, turbine inlet flaps 52, scramjet outlet flaps 56, and turbine outlet flaps 54 selectively control the scramjet flowpath F_(S) and turbine flowpath F_(T) in response to scramjet and turbine operation. Turbine outlet flaps 54 and scramjet outlet flaps 56 selectively controls the turbine flowpath F_(T) so as to provide an efficient nozzle for the scramjet flowpath F_(S). It should be understood that the disclosed embodiment illustrated is merely exemplary and that various engine packages and propulsion systems may be utilized.

Referring to FIG. 2, an electrical power generation system 60 includes a heat exchanger (HEX) 62 adjacent the scramjet flowpath F_(S) to transfer heat from a heat gradient between the atmosphere and combustion gases to pre-combustion scramjet fuel. The HEX 62 may be located anywhere along the scramjet flowpath F_(S), where sufficient delta temperature can be realized, such as adjacent the inlet, isolator, combustor 38 or nozzle. For an exemplary hydrocarbon based liquid fuel such as JP 8, JP 7 or methane, the HEX 62 may be a liquid-gas heat exchanger. Alternatively, the exemplary fuel may be hydrogen gas and the heat exchanger a gas-gas heat exchanger.

The HEX 62 includes an upstream fuel inlet 64 and a downstream fuel outlet 66. In the exemplary embodiment, the inlet 64 may be upstream of the combustor 38 along the scramjet flowpath F_(S) because pre-combustion aerodynamic heating may be relevant. A fuel flowpath 68 for the scramjet fuel extends from a tank 70 to a fuel pump 72 and then to the inlet 64. After exiting the outlet 64, heated fuel is communicated along the fuel flowpath 68 to a fuel distribution valve network 74 and then to the combustor 38. The fuel distribution valve network 84 distributes fuel to various combustor injection locations for various purposes such as pilot flow, main combustion flow, and staging. Variations for cooling the engine include multiple inlet and outlet networks, circumferential coolant flow and coolant flow from downstream to upstream.

The HEX 62 is in communication with at least one thermoelectric device (TED) 80. The HEX 62 and the TED 80 may be located adjacent the scramjet flowpath F_(S) and adjacent a vehicle external skin structure 82 to take advantage of the waste heat, high thermal gradients, and available, unused volume that typically exist therein. The vehicle external skin structure 82 may include various vehicle structure and is representative of various vehicle locations such as the engine package 20. The vehicle external skin structure 82 is exposed to atmosphere and thus aerodynamic heating.

The TED 80 may be coupled to an electrical power conditioning, storage, and distribution system 84 which receives raw electrical input and outputs desired conditioned electricity of a constant and proper voltage to drive, for example, the control system 40, fuel pump 72, distribution valve network 74 and similar components associated with the dual mode scramjet engine system 18, as well as other loads 75, including engine and vehicle power requirements for items such as actuators for flaps 50, 52, 54, and 56.

Referring to FIG. 3, the HEX 62 includes a noncomposite support structure 90 and a heat tolerant ceramic matrix composite (CMC) panel 92 such as silicon carbide fibers in a silicon carbide matrix (SiC/SiC); silicon carbide fibers in a silicon-nitrogen-carbon matrix (SiC/SiNC); and melt-infiltrated silicon-carbide-fiber-reinforced silicon carbide (MI SiC/SiC) composite panels. The HEX 62 may be an all-CMC HEX manufactured from a woven preform with a 3-dimensional weave so as to provide high interlaminar mechanical properties and a multiple of fuel cooled channels 86 formed therein. The multiple of fuel cooled channels 86 may be fiber-reinforced by an overbraided fiber braid layer 87. In the consolidation process for the CMC panel 92, the chemical vapor infiltration process (CVI) results in a SiC layer being formed on the inner surface of the channels 86.

The channels 86 are formed by insertion of graphite/epoxy inserts during the weaving process, and thermally decomposing these rods after the MI SiC/SiC consolidation. The channels 86 may be micro-engineered to achieve the desired flow and heat transfer characteristics. Although illustrated as a oval shape cross-section in the disclosed embodiment, may be of any cross-sectional shape such as racetrack, rectilinear, circular, trapezoidal, complex or other such cross-sectional shape. For further understanding of other aspects of the manufacture of such channels, attention is directed to U.S. Pat. No. 6,627,019, issued Sep. 30, 2003, “Process for Making Ceramic Matrix Composite Parts with Cooling Channels” which is assigned to the assignee of the instant invention and which is hereby incorporated herein in its entirety.

Each of the multiple of fuel cooled channels 86 may alternatively or additionally include a metallic tubular liner 88. The metallic tubular liner 88 may be inserted into each the multiple of fuel cooled channels 86 after formation thereof.

The noncomposite support structure 90 operates as a structural frame while the heat tolerant CMC panel 92 shields the support structure 90 from the intense heat of the combustion products P to maintain the support structure within operational temperature limits.

A fastener system 94 secures the CMC panel 92 to the noncomposite support structure 90. The fastener system 94 generally includes an internal pocket 96 formed within the CMC panel 92, a fastener stud 98 and foot hardware 100. The fastener stud 98 includes a head 102 and a shank 104 which extends from the head 102. The fastener stud 98 may be manufactured of metal or CMC. If CMC, the fiber architecture of the fastener can be controlled independent of the component fiber architecture. The foot hardware 100 may include a threaded nut, a spring, a collar developed for Miller fasteners, or other such attachment hardware.

The fastener stud 98 is inserted into the internal pocket 96 such that the fastener head 102 fits through a pocket opening 100A (FIG. 4A) then rotated and loaded (FIG. 4B) by the foot hardware 100 so as to secure the CMC HEX panel 92 to the noncomposite support structure 90. The fastener system 94 provides interlaminar properties, minimizes gas leakage, minimizes tolerance issues and does not even project through the CMC HEX panel 92 which thereby assures operation in a flush configuration.

Referring to FIG. 5, another fastener system 94A “z” utilizes a fastener stud 98A that is received within one 86′ of the multiple of fuel cooled channels 86′ of the CMC HEX 62′. The one of the multiple of fuel cooled channels 86′ may be a non-coolant fluid channel. Alternatively, a seal arrangement 106 may be located about the shank 104A such that even the fuel cooled channel 86′ which receives the fastener stud 98A may also be utilized for coolant fluid communication.

Referring to FIG. 6A, another fastener system 94B “z” utilizes the metallic tubular liner 88′ as the fastener head 102B. The metallic tubular liner 88′ forms the fastener head 102B while a multiple of extensions such as rods which are welded or brazed to the metallic tubular liner 88′ (FIG. 6B) form the fastener shanks 104B. The metallic tubular liner 88′ slide into the one 86′of the multiple of fuel cooled channels 86 formed therein while the fastener shanks 104B slide through a longitudinal pocket opening 100A.

Referring to FIG. 7A, another fastener system 94C “z” is utilized with a Maintainable Composite Panel (MCP) HEX 110. The MCP HEX 110 utilizes a CMC (carbon-carbon) hot-face 112 which may be readily disassembled from a multiple of metallic coolant tubes 114, a thermal insulation panel 116 and a support structure 118 (FIG. 7B). The MCP HEX 110 facilitates maintenance and enhances the reusability of particular components.

The fastener system 94C utilizes fastener studs 120 generally as described above with an extended fastener shank 122 to assemble the MCP HEX 110 (FIG. 7C).

It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.

It should be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit from the instant invention.

Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.

The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The disclosed embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention. 

1. A heat exchanger system comprising: a CMC HEX panel having an internal pocket formed therein, said internal pocket having at least one pocket opening in communication with said internal pocket which extends through an outer surface of said CMC HEX panel.
 2. The system as recited in claim 1, further comprising a fastener stud which defines a head and a shank, said head receivable within said internal pocket for rotation therein between an engaged and a disengaged position.
 3. The system as recited in claim 2, wherein said fastener stud head is 2-dimensional in shape.
 4. The system as recited in claim 3, wherein a lateral cross-section of said internal pocket corresponds to said fastener stud head.
 5. The system as recited in claim 2, wherein said fastener stud receives a foot hardware assembly to mount said CMC HEX panel to a support structure.
 6. The system as recited in claim 1, wherein said CMC HEX panel includes a multiple of coolant channels formed therein.
 7. The system as recited in claim 6, wherein said internal pocket is formed by at least one of said multiple of coolant channels.
 8. The system as recited in claim 7, wherein said internal pocket includes a metallic tubular liner.
 9. The system as recited in claim 7, wherein said metallic tubular liner includes a multiple of fastener shanks which extend transversely therefrom.
 10. A heat exchanger system assembly comprising: a CMC HEX panel having an internal pocket formed therein, said internal pocket having at least one pocket opening in communication with said internal pocket which extends through an outer surface of said CMC HEX panel; a support structure; and a fastener system that secures said CMC HEX panel to said support structure, said fastener system includes a fastener stud which defines a fastener stud head and a fastener shank, said fastener stud head receivable within said internal pocket through said pocket opening for rotation within said internal pocket between an engaged and a disengaged position, said support structure mounted to said fastener shank.
 11. The system as recited in claim 10, wherein said CMC HEX panel includes a multiple of coolant channels formed therein.
 12. The system as recited in claim 11, wherein said internal pocket is formed by at least one of said multiple of coolant channels.
 13. The system as recited in claim 12, wherein said internal pocket includes a metallic tubular liner.
 14. The system as recited in claim 13, wherein said metallic tubular liner includes a multiple of fastener shanks which extend transversely therefrom.
 15. The system as recited in claim 10, further comprising a multiple of metallic coolant tubes sandwiched between said CMC HEX panel and said support structure.
 16. A Maintainable Composite Panel heat exchanger system assembly comprising: a CMC HEX panel having an internal pocket formed therein, said internal pocket having at least one pocket opening transverse to said internal pocket which extends through an outer surface of said CMC HEX panel; a support structure; a multiple of metallic coolant tubes; and a fastener system that secures said CMC HEX panel to said support structure, said fastener system including a fastener stud which defines a fastener stud head and a fastener stud shank, said head receivable within said internal pocket for rotation therein between an engaged and a disengaged position, said support structure mounted to said fastener shank to at least partially sandwich said multiple of metallic coolant tubes between said CMC HEX panel and said support structure.
 17. The system as recited in claim 16, further comprising a thermal insulation panel sandwiched between said multiple of metallic coolant tubes and said support structure.
 18. The system as recited in claim 16, wherein said fastener stud head is 2-dimensional in shape.
 19. The system as recited in claim 18, wherein a lateral cross-section of said internal pocket corresponds to said fastener stud head.
 20. The system as recited in claim 18, wherein said shank extends between two of said multiple of metallic coolant tubes. 